Means for resiliently mounting tubular members



Jun 3, 1969 s. P. JQNES 3,447,603

MEANS FOR RESILIENILY MOUNTING TUBULAR MEMBERS I Filed July 31 1967 LLLULlLlL LLLH III

INVENTOR SAMUEL P. IONES ms ,moamv United States Patent 0 3,447,603MEANS FOR RESILIENTLY MOUNTING TUBULAR MEMBERS Samuel P. Jones, Erie,Pa., assignor to General Electric Company, a corporation of New YorkFiled Juiy 3, 1967, Ser. No. 651,040

Int. Cl. F28f 9/04; F161 39/04, 27/00 US. Cl. 165178 10 Claims ABSTRACTOF THE DISCLOSURE A tube sheet for a heat exchange device whereinsleeves are resiliently mounted within a plurality of larger openingsprovided in a perforated metal sheet with an elastomeric material. Thesurface of the elastomeric material opposite the perforated member isrendered vapor-impervious by application thereto of a layer of asuitable vapor-impervious material.

This invention relates to means for mounting tubular members and moreparticularly to a new and improved means for mounting the ends thereofto allow some freedom of movement of individual members relative to eachother. While the following disclosure particularly relates the inventionto heat exchange devices (i.e., radiators) for internal combustionengine cooling systems, it will be obvious that the invention is notthus limited, and may for example, be employed on other types ofapparatus or one heat exchange devices for other types of systemswithout departing from the spirit or scope thereof.

Heat exchange devices are frequently made up of a plurality of parallelradiating, or heat exchange, tubes extending between, and rigidlysecured to, a pair of headers, more commonly referred to in the art astube sheets. Often these tube sheets can be made thin so as to flexslightly with changes in length of the radiating tubes due to thealternate expansion and contraction thereof under varying operatingtemperatures, to avoid damage to the tubes or other portions of the heatexchange device.

When a large temperature difference between adjacent tubes of the heatexchange device occurs, however, very large stresses arise between thetubes and the tube sheets. These stresses are often of suflicientmagnitude to rupture the tube or tube sheet or weaken or break thejoints between the tubes and the tube sheets.

For example, in the cooling system described in United States Patent No.3,067,817, the tubes of the radiator are subjected to such very largevariations in temperature that the usual constructions have not beensatisfactory. In that system, there is either a large stream of coolantflowing from the engine to the radiator or none at all. That is, thereis either no coolant in the radiator, and the tubes, without coolanttherein, are subjected to the surrounding outside ambient temperature,which may be as low as about -60 F., or the radiator is subjected to alarge flow of coolant which may be at a temperature as high as about185200 F. Moreover, this hot coolant does not instantaneously reach allradiating tubes or all portions thereof at the same time so thatindividual radiating tubes are subjected to widely varying temperaturesand temperature gradients. For example, some of the radiating tubes maybe rapidly increasing in length due to the presence of the hot coolantwhile other tubes, having no coolant therein, are not changing inlength.

Prior art attempts to solve this problem have not been satisfactory. Forexample, it has been proposed in the prior art British Patent 741,625 toprovide tube sheets with a series of openings each of which included aflange and a cap therefor and into which openings a resilient hollowplug or grommet was inserted. The ends of the radiating tubes were theninserted into the hollow plugs or grommets to provide a resilientconnection between the radiating tube and the tube sheets. Although sucha mounting means allows for increases and decreases in length of theradiating tubes by allowing for sliding movement of the tubes throughthe grommet, such a construction has not been entirely satisfactory. Forexample, although a satisfactory mechanical connection can be achievedbetween the grommet, the tube, and the tube sheet, the liquid sealbetween the grommet and the tube has not been entirely satisfactory.

It has also been proposed to employ tube sheets of a rubber composition.For example, one such arrangement was disclosed in United States PatentNo. 2,240,537, Young, wherein a plurality of sleeves are vulcanized intoa tube sheet of a rubber composition; the sleeves having openingstherein which are adapted to receive the ends of the radiator tubes.Because the entire tube sheet is made of resilient material (rubber) theradiator tubes are free to expand and contract individually and any tubevibrations pass into the rubber tube sheet and are absorbed thereby.Although such an arrangement provided for a satisfactory liquid tightseal which accommodated individual tube movement, the sheet itself wasnot mechanically strong enough to prevent sagging so that in anyradiator of large size some additional reinforcing means was required.Also, the usual distortion, shrinkage and the like which took place whenthe rubber tube sheet was cured so varied the pattern of the sleevesthat assembly of the radiator tubes into such sleeves was not onlyextremely diflicult, but sometimes impossible.

It has been discovered that the foregoing manufacturing and operatingdifficulties could be obviated by employing a construction employing arigid tube sheet having openings punched, or otherwise providedvtherein, in a desired pattern into which openings the sleeves weresuitably resiliently secured as by an elastomeric material suitablybonded to the tube sheet and the sleeve. This allowed the pattern to bemaintained during curing so that the heat exchanger tubes could bereadily installed in the sleeves and also provided a mechanically rigid,selfsupporting tube sheet which allowed for individual movement of thetubes secured thereto. In spite of this, the foregoing structure stillfailed to provide a heat exchange device which had an entirelysatisfactory operating lifetime, and this was most especially so insevere operating environments such as that to which the radiator for alocomotive cooling system of the type described in the United StatesPatent No. 3,067,817 would be subjected. For example, under actualoperating conditions, liquidfilled blisters were found to form in theelastomeric material and, since rupture of such blisters could result ina leak, this condition may result in premature failure of the radiator.

It is an object of this invention, therefore, to provide a new andimproved tube sheet arrangement for heat exchange devices whichsubstantially overcomes one or more of the prior art difiiculties andexhibits increased operating lifetime.

It is another object of this invention to provide a new and improvedtube sheet arrangement for heat exchange devices which exhibitsmechanical rigidity while at the same time, allowing for individualmovement of the tubular members mounted thereto, exhibits long operatinglifetime, reduced maintenance and which does not require complex andexpensive manufacturing procedures.

In its broader aspects, the present invention provides for a new andimproved tube sheet arrangement of the type wherein sleeves areresiliently mounted within openings in a rigid reinforcing member andwherein the surface of the elastomeric material exposed to the heated 3fiuid of the system is smaller than the surface area exposed to theambient temperature.

Briefly stated, in accordance with one aspect of this invention, a newand improved tube sheet for a heat exchange device comprises aperforated member of metal or other suitable material exhibiting therequired amount of structural integrity to provide a heat exchanger tubesheet. The perforated member is provided with a plurality of largeropenings therein arranged in a preselected pattern so that one openingis provided for each of the radiating tubes of the heat exchange device.A plurality of sleeves are also provided one of which is positionedwithin each of the openings and resiliently secured therein by anelastomeric material which is intimately and irreversibly bonded to thesleeves and to the perforated member. The sleeves have an outsidedimension smaller than the openings in the perforated member and areadapted to embrace an end of a radiating tube and be suitably securedthereto so that the radiating tubes are thus arranged to be resilientlymounted to the perforated memher. The surface of the elastomericmaterial remote from the perforated member is rendered vapor-imperviousin any suitable manner such as by bonding thereto at least one layer ofa suitable vapor-impervious material, such as metal, a fluorocarbonmaterial or the like or the group consisting of polytetrafluoroethylene,polytrifluorochloroethylene, combinations thereof and materials treatedtherewith.

The novel features believed characteristic of this ininvention are setforth with particularity in the appended claims. The invention itself,however, together with its organization and method of operation willbest be understood by reference to the following description taken inconjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of a heat exchange device incorporatingthis invention with the inlet and outlet tanks and ductwork removed;

FIG. 2 is a partial sectional view of one embodiment of the tube sheetconstruction of this invention; and

FIG. 3 is a top view of the perforated member showing the small openingsof the member and the larger openings provided therein in the desiredpattern.

In FIG. 1 there is shown a portion of a heat exchange device with inletand outlet tanks and all external ductwork removed. The portion of theheat exchange device is generally designated and comprises a pluralityof heat exchange, or radiating, tubes 11 extending between two tubesheets 12 and 13. The tube sheets 12 and 13 are adapted to connect toinlet and outlet tanks respectively, so that one fluid, such as waterfor example, may be circulated through the tubes and a second fluid,such as air, may be circulated externally of the tubes. In order toincrease the heat exchange between the fluids, the radiating tubes aregenerally provided with external fins 14.

In accordance with this invention, means are provided for resilientlymounting the radiating tubes between the inlet and outlet tanks to allowfor individual changes in their lengths under varying temperatureconditions while maintaining a perfect and positive liquid seal at alltimes. To this end, I have provided means for rigidly securing the endsof the radiating tubes to a short metal sleeve, or ferrule, whichferrule has been resiliently mounted by bonding it intimately to aregion of an elastomeric material. The details of the tube sheet inaccordance with one embodiment of this invention are shown more clearlyin the enlarged portion of tube sheet 13 illustrated in FIG. 2.

Preferably, the novel tube sheet arrangement of this invention isemployed at both ends of the radiating tubes although for manyapplications, satisfactory results may be achieved by providing suchtube sheet at only one end.

As shown in FIG. 2, the tube sheet arrangement of this inventionincludes a number of sleeves, or ferrules, 15 which are intimately andirreversibly bonded within the larger openings 16 punched, or otherwisesuitably provided, in a preselected pattern in a perforated member 18 byan elastomeric material 20. The relation between the openings making upthe perforated member 18 and the larger openings 16 is shown moreclearly in FIG. 3. The ends of the radiating tubes extend through thesleeves 15 and are rigidly secured thereto, such as by soldering,brazing, welding, expanding or any other suitable means of providing arigid, leakproof connection. In accordance with this invention, at leastthe major portion of the surface of the elastomeric material 20 oppositethe perforated member 13, and preferably the entire portion of suchsurface, is rendered vapor-impervious. Conveniently, this may beprovided by applying to such surface a layer 22 of a suitablevapor-impervious material such as a metal, a fluorocarbon polymer orother suitable material. Although the precise nature of theliquid-filled blister formation in the elastomeric material in the'priorconstruction is not as yet fully understood, it is believed to be due tomoisture vapor absorbed by the elastomeric material which vapor thencondenses as it nears the cool surface of the rigid reinforcing plate.

In accordance with this invention, therefore, a tube sheet arrangementis provided wherein the surface area of the elastomeric material exposedto the hot fluid is smaller than the surface area exposed to the outsideambient temperature. This is accomplished in one embodiment by providingthe reinforcing member with many small perforations and applying avapor-impervious layer to the surface of the elastomeric material.

The layer 22 should be capable of withstanding the extremes oftemperature to which the tube sheet is subjected during operation aswell as during its manufacture. For example, if the radiating tubes 11are to be secured into the sleeves 15 by means of a roller expandingoperation, the outer layer 22 of vapor-impervious material need only berequired to withstand the extreme operating temperatures. On the otherhand, if the tube ends are to be secured into the sleeves 15 by asoldering operation, such as a dip soldering technique for example, theouter layer 22 (and the elastomeric material itself) must be capable ofwithstanding the soldering temperature (e.g., 550 F.) for the timenecessary to make the connection.

The large openings 16 in the perforated member 18 are made larger thanthe outside dimension of the sleeve 15 and are arranged in a patternapproximately the same as that desired for the radiating tubes to bemounted. In this way, the tube sheet, with sleeves 15 resilientlymounted within the large openings 16, may easily fit about the ends ofthe tubes which are thereafter rigidly secured to the sleeves. Forexample, the perforated member 18 may be disposed in one section of asuitable mold with the sleeves 15 positioned within the large openings16. The elastomeric material is then introduced under suitable heat andpressure to provide the required intimately bonded resilient connectionbetween the sleeves 15 and the perforated member 18. Also, theelastomeric material may be extended over the entire perforated member18 as shown so as to serve as a suitable gasket between the tube sheetand the tank to which it is to be connected. The vapor-impervious layer22, which for example, may be a thin sheet of etched Teflon havingopenings suitably provided therein to fit about the sleeves 15, may bebonded to the surface of the elastomeric material 20 during theforegoingmolding operation. Alternatively, the elastomeric material may be moldedinitially to provide for the resilient bonding of the sleeves to theperforated member and the thin sheet of vaporimpervious materialthereafter bonded to the surface. For example, the tube sheet may beinitially molded and the mold thereafter opened and a thin sheet of avapor-impervious material, such as etched Teflon, having openingssuitably provided for therein to fit about'the sleeves 15, placed on thesurface of the elastomeric material. The mold is then closed again andthe vapor-impervious material bonded to the surface of the elastomericmatemounted within the large openings in the perforated member such asby molding the elastomeric material to the sleeves under suitable heatand pressure, and heat curing if required, in accordance with standardmolding and bonding procedures not requiring complex or expensivetooling. Also, either at the same time or during a subsequent procedure,the vapor-impervious layer 22 may be applied. The ends of the radiatingtubes are then rigidly secured to the sleeves in any suitable manner. Inthis respect, for example, it is only necessary that some means heprovided for effecting a rigid, leakproof connection between theradiating tube and the sleeves and any suitable means for accomplishingthis may be employed. Conveniently, the end of the respective radiatingtubes may extend into or through the sleeves and the rigid leakproofconnection made in a manner which may be the same as that used in thepast in rigidly securing the ends of the radiating tubes to theconventional metal tube sheet. Alternatively, a suitable butt-typeconnection may be made between the end of the tube and the sleeve. Thus,a rigid, leakproof connection is provided between the end of the tubeand the sleeve and a resilient, leakproof, intimately bonded connectionis provided between the sleeve and the region of the elastomericmaterial which connects the sleeve to the perforated member.

Any elastomeric material which effects an intimate bond to metal, eitherwith or without the use of a primer or other bonding agent and which iscapable of resisting the fluid employed in the heat exchange system issuitable for use in this invention. Among some of the suitable preferredmaterials for use in this invention, for example, are silicone rubber,natural rubber and synthetic rubber, such as polychloroprene rubber,butyl rubber and ethylene-propylene copolymer rubber. One elastomericmaterial which provided especially satisfactory results was compoundedfrom a silicone rubber gum sold by the General Electric Company,Silicone Products Department, under the designation No. CE-407. Suchmaterial is self-bonding and provides a very strong intimate, andirreversible bond to the metal sleeves and the material of theperforated member 18, which bond is not affected by the coolant at thetemperatures encountered, for example, in locomotive engine coolingsystem shown and described in United States Patent No. 3,067,817.

While only certain particular embodiments of the invention have beendescribed in detail herein, it will be apparent to those skilled in theart that many changes and modifications may be made without departingfrom the invention in its broader aspects. It is intended, therefore, inthe appended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a heat exchange device of the type comprising a plurality ofradiating tubes extending from and secured to at least one tube sheet soas to define a cooling region and wherein the side of said tube sheetremote from said cooling region is exposed to the heated fluid of theheat exchange system; a tube sheet comprising:

(a) a plurality of sleeves adapted for rigid connection to saidradiating tubes;

(b) a reinforcing member having a plurality of openings;

(c) an elastomeric material intimately and irreversibly bonded to saidsleeves and to the one side of said reinforcing member which is exposedto the heated fluid of the heat exchange system;

(d) said sleeves having an Outside diameter smaller than that of saidopenings and being resiliently mounted within the openings at saidreinforcing member by said elastomeric material; and

(e) means for providing that the major portion of the surface area ofthe elastomeric material directly exposed to the heated fluid of theheat exchange system is rendered vapor impervious.

2. The tube sheet of claim 1 wherein said reinforcing member is aperforated member having large openings provided therein for saidsleeves and the surface of said elastomeric material is renderedvapor-impervious.

3. The tube sheet of claim 2 wherein the surface of said elastomericmaterial is rendered vapor-impervious by a layer of vapor-imperviousmaterial in intimate association therewith.

4. The tube sheet of claim 3 wherein said layer of vapor-imperviousmaterial is metal.

5. The tube sheet of claim 3 wherein said layer of vapor-imperviousmaterial is a fluorocarbon polymer.

6. The tube sheet of claim 3 wherein said layer of vapor-imperviousmaterial is a material selected from the group consisting ofpolytetrafluoroethylene, polytrifluorochloroethylene, combinationsthereof and materials treated therewith.

7. The tube sheet of claim 1 wherein said reinforcing member is aperforated metal plate having large openings provided therein and alayer of metal is intimately and irreversibly bonded to the surface ofthe elastomeric material.

8. The tube sheet of claim 1 wherein said elastomeric material is aself-bonding silicone rubber compound.

9. The tube sheet of claim 8 wherein said reinforcing member is aperforated member having larger openings provided therein to receivesaid sleeves and a layer of metal is bonded to the surface of saidsilicone rubber compound.

10. The tube sheet of claim 8 wherein said reinforcing member is aperforated member having larger openings provided therein to receivesaid sleeves and there is bonded to the surface of said silicone rubbercompound a layer of vapor-impervious material selected from the groupconsisting of polytetrafluoroethylene, polytrifluorochloroethylene,combinations thereof and materials treated therewith.

References Cited UNITED STATES PATENTS 2,240,537 5/1941 Young -832,686,767 8/1954 Green 260-296 2,689,805 9/1954 Groze 117-227 3,001,7669/1961 Laist 165-178 3,108,898 10/1963 Nitzsche 156-329 3,315,740 4/1967Withers 165-178 X 3,092,360 6/1963 Cook et al. 285-158 X ROBERT A.OLEARY, Primary Examiner.

THEOPHIL W. STREULE, Assistant Examiner.

US. Cl. X.R. 165-69; 285-158

